A Multiscale Modeling Framework for Predicting Bone and Cartilage Stress
in Patients with Patellofemoral Pain Syndrome
Pal,
1
S;
Besier,
2
TF ;
1Stanford
Draper,
1
CE ;
University, CA;
Gold,
2 University
1
GE ;
Fredericson,
of Auckland, NZ;
3VA
1
M;
Delp,
1
SL ;
and Beaupré,
1,3
GS
Rehab. R&D Center Palo Alto, CA
Purpose: To determine patellofemoral (PF) stress during activities of daily living using patient-specific computational modeling.
Imaging
Whole Body Simulations
Motion Analysis
Force
Raw VL
Raw VM
Raw EMG
Filtered EMG
C
A
B
A
C
We acquired 3D knee geometry of subjects using a combination of
(A) supine, high resolution MRI and (B) PET/CT imaging. We
acquired in vivo kinematics by registering the models to upright,
weightbearing MRI (C). The hotspot on the PET/CT image
indicates region of elevated bone metabolic activity.
B
Stance
Length
Filtered VL
C
Filtered VM
A
Swing
We analyzed the motion of subjects while performing activities of
daily living, including (A) upright, weightbearing squat and (B)
walking. We recorded muscle electromyography (EMG) activations
during the functional tasks (C).
B
Musculotendon actuator
We created subject-specific simulations of activities of daily living
(A, B) using an EMG-based musculoskeletal model (C). The
musculoskeletal model included a Hill-type muscle actuator and
EMG-to-activation dynamics.
PF Joint Simulations
Result: Gender Differences
Result: Predict Clinical Outcomes
Females
High
Males
3
2
Low
1
A
B
C
0
1.5
Pre
Post
300
Post
200
Pre
Symptomatic
100
Females with PF pain have greater patellar cartilage stress than
males with PF pain (p = 0.02). This may explain the greater
prevalence of PF pain in females compared to males.
1.0
0.5
VM+15%
VM+30%
0.0
0
0
We developed patient-specific finite element models of the PF joint (A). We
determined bone and cartilage stress during activities of daily living (B, C). We
assigned cartilage material properties based on experimental studies, and bone
material properties based on PET/CT data.
Stress (MPa)
4
*
2 ) 2)
(mm
Area
Contact
(mm
Area
Contact
Strain Energy Density (J/m3)
400
5
Velocity
30
60
Tibia
Flexion
Tibia
Flexion(deg.)
(deg.)
0
30
60
Tibia Flexion (deg.)
A vastus medialis muscle strengthening intervention resulted in
increased contact area and decreased PF stress. This is a
personalized medicine approach to treatment of PF pain.
Public health relevance: Patellofemoral pain syndrome is common, affecting millions of individuals nationwide and costing billions in health care
spending. Current treatment methods are unpredictable and often unsatisfactory as this syndrome has many possible causes that are difficult to
diagnose. The goal of our study is to understand the mechanisms underlying PF pain and improve the efficacy of clinical outcomes.
Acknowledgements: NIH (U54 GM072970, EB005790-05); VA Rehab. R&D Service (A2592R)
The NIH National Center for Physics-based Simulation of Biological Structures